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What is human growth hormone?

To begin with, the human growth hormone is also called somatotrophin a peptide hormone secreted by the anterior lobe of the pituitary gland.

It stimulates the growth of essentially all tissues of the body, including bone.

GH is synthesized and secreted by anterior pituitary cells called somatotrophs, which release between one and two milligrams of the hormone each day.

GH is vital for normal physical growth in children; its levels rise progressively during childhood and peak during the growth spurt that occurs in puberty.

Growth hormone deficiency

GH deficiency is one of the many causes of short stature and dwarfism.

It results primarily from damage to the hypothalamus or

To the pituitary gland during fetal development (congenital GH deficiency) or following birth (acquired GH deficiency).

GH deficiency may also be caused by mutations in genes that regulate its synthesis and secretion.

Mutations in these genes may also cause decreased synthesis and secretion of other pituitary hormones.

In some cases, GH deficiency is the result of GHRH deficiency, in which case GH secretion may be stimulated by infusion of GHRH.

Other cases, the somatotrophs themselves are incapable of producing GH, or

the hormone itself is structurally abnormal and has little growth-promoting activity.

In addition, short stature and GH deficiency are often found in children diagnosed with psychosocial dwarfism, which results from severe emotional deprivation.

Functions of the human growth hormone

GH stimulates protein synthesis and increases fat breakdown to provide the energy necessary for tissue growth.

It also antagonizes (opposes) the action of insulin.

GH may act directly on tissues, but much of its effect is mediated by stimulation of the liver and other tissues to produce and release insulin-like growth factors, primarily insulin-like growth factor 1 (IGF-1; formerly called somatomedin).

Growth hormone excess

Excess GH production is most often caused by a benign tumour (adenoma) of the somatotroph cells of the pituitary gland.

Some cases, a tumour of the lung or of the pancreatic islets of Langerhans produces GHRH, which stimulates the somatotrophs to produce large amounts of GH.

In rare cases, ectopic production of GH (production by tumour cells in tissues that do not ordinarily synthesize GH) causes an excess of the hormone.

Somatotroph tumours in children are very rare and cause excessive growth that may lead to extreme height (gigantism) and features of acromegaly.

Acromegaly refers to the enlargement of the distal (acral) parts of the body, including the hands, feet, chin, and nose.

The enlargement is due to the overgrowth of cartilage, muscle, subcutaneous tissue, and skin.

Thus, patients with acromegaly have a prominent jaw, a large nose, and large hands and feet, as well as enlargement of most other tissues, including the tongue, heart, liver, and kidneys.

In addition to the effects of excess GH, a pituitary tumour itself can cause severe headaches, and pressure of the tumour on the optic chiasm can cause visual defects.